This invention relates to fastener driving tools and, more particularly, to fastener driving tools including an indicator for signalling the operator that the operator may be missing the substructure intended to be fastened or that the tool is being supplied by too great air pressure and is overdriving.
The type of fastener driving tool hereto contemplated typically includes a fastener driving element or driver which is mounted within a drive track within which successive fasteners are fed. The driver is mounted for movement through repetitive cycles, each of which includes a drive stroke during which the fastener is moved out of the drive track into the work piece and a return stroke. The fastener driving element is fixedly connected with a piston which is mounted within a cylinder for movement through a drive stroke and a return stroke with the fastener driving element. The piston is driven preferably by compressed air applied to an operative surface of the piston. The fastener driven by the driving element absorbs most of the tool energy. The remainder of the tool energy is absorbed by the tool, primarily through an annular bumper of resilient material mounted in a position to be engaged by the piston and defining the end the drive stoke thereof. Substantially different fastener driving forces are required to drive a fastener due to variances in wood type, moisture or knots in the substructure to be nailed. For example, where soft wood underlies a fastener position, only a light driving force is required to fully seat the fastener. When harder wood or knots underlie a fastener position, much greater forces are required for similar results. In addition, if a stud or joist substructure is missed, the tool may be operated with such a force so as to cause overdriving. If a tool is operated continuously in an overdriving manner, the life of the tool is shortened. Further, when the substructure is missed, fasteners are wasted and do not perform their function of coupling to the substructure, which increases costs and reduces productivity.